1. Field of the Invention
The present invention relates to an image capture device defective pixel detection device adapted to correct defective pixels among a plurality of pixels making up the pixels of an image captured by the image capture device, and which may result for example from improper operation of image capture elements provided to the imaging device.
2. Description of the Related Art
Image capture devices such as digital still cameras and digital video cameras have come to enjoy widespread use in recent years. Such image capture devices employ image capture elements that are adapted to convert light received via a lens into an electrical signal. CCD (Charge Coupled Device), CMOS (Complementary Metal Oxide Semiconductor) sensors, and the like are commonly used image capture elements of this kind. Such image capture elements are furnished with a plurality of photodetector elements (photodiodes) corresponding to the plurality of pixels that make up the photographed image, and are adapted to output image data that represents a respective pixel value of each pixel. When an image taken by an image capture device is displayed on a display device, if for example any of the photodetector elements should experience improper operation during shooting, resulting in output of pixel data of a higher value than the correct value for output, the pixel corresponding to the photodetector element in question may appear as a so-called bright defect, whereas if pixel data of a lower value than the correct value for output is output, the pixel corresponding to the photodetector element in question may appear as a so-called dark defect.
Various technologies have been proposed in the past for use in image capture devices, for the purpose of detecting defective pixels caused for example by improper operation of an image capture elements among a plurality of pixels making up the pixels of an image captured by the device. For example, Patent Citation 1 (JP-A 2001-86517) discloses technology whereby in the event that a bright defect which constitutes a pixel defect is detected in a single-plate type color video camera, a check is made to ascertain, from the frequency characteristics of a neighboring pixel having a different color filter from the color of the pixel under examination, that the examined pixel does not have a high-frequency component; then, if it is detected that the examined pixel has a high-frequency component, designating the pixel to have a defect.
Patent Citation 2 (JP-A 2002-344814) discloses technology whereby during shooting, pixel blocks composed of nine (3×3) pixels centered on a pixel of interest are sequentially accumulated in a buffer; the values of the pixel of interest and its neighboring pixels are compared while counting the number Hn of neighboring pixels with higher values than the pixel of interest and the number Ln of neighboring pixels with lower values than the pixel of interest; and in the event that the number Hn of neighboring pixels with higher values than the pixel of interest is five or more, determining that a dark defect has occurred, and outputting the pixel of interest after first replacing its value with the average value of the neighboring pixels having higher values; or in the event that the number Ln of neighboring pixels with lower values than the pixel of interest is five or more, determining that a bright defect has occurred, and outputting the pixel of interest after first replacing its value with the average value of the neighboring pixels having lower values.
However, the technologies taught in the above Patent Citations 1 and 2 have the problem that if a defective pixel is located within a pattern of a subject having minimal color variation, the defect produced thereby will be particularly noticeable. In such cases, lowering the threshold value so as to be able to detect more defective pixels will create the problem of degrading the picture quality of high-definition patterns that include edges.